The present invention relates to a photoelectric semiconductor device and, more particularly, to a dual junction photoelectric semiconductor device including at least two P-N junctions formed at different depth from the surface of the semiconductor device.
It is well known in the art that the photoelectric conversion phenomenon is observed when a light beam impinges on a semiconductor element including a P-N junction. This photoelectric conversion phonomenon is utilized in various semiconductor devices such as phototransistors, photodiodes and solar batteries.
The light absorption factor is greatly influenced by the material of the semiconductor substrate and the wavelength of the light beam impinging thereon. The light beam of a shorter wavelength is absorbed near the surface of the semiconductor substrate, whereas the light beam of a longer wavelength reaches a deeper section.
Accordingly, an object of the present invention is to provide a dual junction photoelectric semiconductor device including two P-N junctions at different depth from the surface of the semiconductor substrate.
Another object of the present invention is to enhance the spectral sensitivity of a desired wavelength range in a photoelectric semiconductor device.
Still another object of the present invention is to provide a photoelectric semiconductor device including at least two pairs of output terminals for developing output signals derived from at least two P-N junctions formed in the photoelectric semiconductor device.
Yet another object of the present invention is to provide a photoelectric semiconductor device which has a linear output characteristic over a wide range of wavelength.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, an N type impurity region is formed in a P type semiconductor substrate to establish a first P-N junction. A P type impurity region is shallowly formed in the N type impurity region to establish a second P-N junction. Output signals are derived from the P type semiconductor substrate and the N type impurity region to form a first photodiode. Output signals are also derived from the N type impurity region and the P type impurity region to form a second photodiode.
In a preferred form, the N type impurity region and the P type impurity region are shunted to reduce the spectral sensitivity in a shorter wavelength zone. In another preferred form, the P type semiconductor substrate and the N type impurity region are shunted to reduce the spectral sensitivity in a longer wavelength zone.